The freedom of movement of the covering board in string instruments is further restricted by a curvature of said board in opposition to the string tension. It necessarily stiffens the covering board in such a way that it is not pressed in by the string tensions. A further restriction to the freedom of movement of the covering board results from the fact that bass bars are required on string instruments for transferring vibrations to the complete covering board surface and for supporting the string tension. A further limitation to the freedom of movement of the covering board and in particular its size and that of the instrument cavity results from the indentations alongside the bridge required for the freedom of movement of the bow in string instruments. In order to permit an adequate movement of the covering board sound holes must be formed between the indentations and the bridge.
The problem of the present invention is therefore to provide an arrangement of the walls and supports in which the string tension introduced via the bridge only insignificantly stresses the sound-emitting walls in the direction of the vibrating movement thereof, the necessary stiffenings only have a minimum detrimental influence on the movements of said walls and a large-volume instrument body is permitted.
The tension of the strings stretched over the bridge is at right angles to the movement direction of the sound-emitting walls of the instrument body, i.e. introduction takes place in the direction of the main plane of these walls. Therefore the walls are not pretensioned in the vibration movement direction and the vibration amplitudes are not limited. These walls do not have to be curved for static reasons. They can be made planar and then vibrate better for the emission of sound. There is also an arrangement of the sound-emitting walls below the strings and the bridge, which obviates any need for an indentation in the walls for the freedom of movement of the bow. Due to the statically stiffer leading off of the string tensions, it is possible to support higher tension levels, the bridge can be made higher and consequently the transmission ratio of the string vibrating movements to the movements of the second-emitting walls can be increased.
As a result of the measures according to the invention for the same excitation energy and vibration energy of the strings, due to larger vibrating walls with larger vibration amplitudes and a larger instrument hollow body, there is a better vibration of the ambient air and consequently more sound can be produced than in comparable string instruments.
The arrangement of the holes 14 in the centre of the hollow body side walls 6 and 9 according to claim 2 gives a maximum spacing between individual holes, considered round the hollow body, whilst simultaneously reducing the bending resistance of the walls. The large reciprocal spacing of the holes prevents an equalization of the pressure of the atmospheric pressure vibrations passing out of the holes around the instrument body to the longwave, low notes, which are lower than in comparable string instruments.
The design of the supports according to claim 3 improves the transfer of the string vibrating movement introduced in punctiform manner onto the upright wall on the upright point of the bridge to the entire surface of the large hollow body sides, without the wide supports restricting the freedom of movement of the sides. The construction of the walls according to claim 4 reduces the moving masses. The construction of the walls according to claims 5 and 6 has the same effect.
The notch in the upright surface of the bridge improves the bendability of the wall along the indicated line. During the further transfer of the string vibrations from the bridge on the upright wall into the supports, said wall is bent along this line. The smaller the wall stiffness at this point, the less impedance to the transfer of the string movements.